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Variable frequency drive for injection molding machine


Currently, most of the injection molding machines are belong to hydraulic transmission, hydraulic drive system is powered by a motor drives a pump. In the changes of injection cycle, the injection molding machine needs different flow and pressure in different processes, it rely on the flow valve and pressure valve to regulate the flow and pressure in different processes. Due to the load has big changes, the metering pump can't adjust output power, so the excess energies are out of the baffle, oil leakage and the oil consumption during the temperature rise period, it exacerbates the valves abrade easily, and cause the oil temperature goes high, motor noise goes loud, and shorten the whole mechanical life. And usually the motor power is higher than actual power, it causes a waste of electricity energy. Hence the AC drives in the injection mold machine application has significant effect for reducing energy waste.

1.Injection molding machine principle
Generally, injection molding process is divided into the following steps: Clamping → injection holding pressure → melt feeding → cooling → mold thimble. Every step completion has time, pressure, speed and position parameters, it mean every position has a corresponding pressure and velocity, and in different location and time, pressure and speed is variable. Meanwhile, the termination signal is sent to the program controller after every step finished, and the program controller send next command after receive signal.

2. Variable frequency for energy saving of injection molding machine
The oil is supplied by quantitative pump in conventional injection molding machine, it needs different speed and pressure in every injection action. In the whole process, the motor speed is constant, so the oil supply is fixed. Due to every action has a interval and not in full load all the time, therefore quantitative oil supply is a waste, according to the measured it's at least about 50%. Variable frequency energy saving is to solve this waste, the AC drive detects the proportional pressure and flow signals from the injection molding machine in real time, and control motor speed according to work status (i.e. flow regulation), to make the flow and pressure just suitable for the needs of the system. Plus, during the non-action status when in cooling period, make the motor stop running, then the electricity energy saving percent increases, to bring significant energy saving effect for injection mold machine with variable frequency.

3. Variable frequency adjust speed control system
Adopting senseless vector frequency technology, the variable frequency drive detects pressure and flow signal from the injection molding machine in real time, disc machine pressure or flow signal is 0 - 1A, outputs different frequency after internal processing to adjust motor speed. i.e.: control output power is synchronization automatic tracking with pressure and flow, means quantitative pump change into energy-saving variable pump.